Build a household water estimate
Start with activities you can count: showers, toilet flushes, taps, laundry and dishes. Separate per-person activities from appliances shared by the household.
Count the activities
For a flow-based activity, liters equal liters per minute multiplied by minutes, occurrences per person per day and people. Four people each taking one six-minute shower at 8 L/min use 192 L/day, or 5.76 m³ over 30 days.
Separate shared appliances
For a fixed-volume event, set volume per event and multiply by occurrences and people. A shared washing machine should use one person in the model, with the household’s total cycles per day. Add activity totals when building a complete estimate.
Reconcile with the meter
This model estimates the selected activity, not all indoor and outdoor consumption automatically. Compare the sum with meter readings. A gap may reflect irrigation, uncounted uses, inaccurate flow assumptions or a leak.
Make an inventory you can check
List each activity with the source of its flow or cycle volume. Separate a normal week from guests and outdoor watering. Where safe, measure a representative tap setting with a known container and elapsed time instead of assuming maximum fixture flow. For each shared activity, record the household total once. Keep a separate list of uses omitted from the estimate so that a later meter comparison has a clear starting point.
Household Water Usage Calculator
Worked example: Build a four-person household water estimate
Related reading: A practical investigation of an unexpectedly high water bill
Reference: EPA WaterSense: understanding your water bill.